Method of processing a spent copper etching solution for reuse in an electroless copper recovery baths

ABSTRACT

Process improvements are described for obtaining long term stability during the electroless recovery of etched copper from a spent acidic copper chloride etching solution having a large concentration of a CuCl component. The spent solution is enriched by the addition of copper ions which are oxidized in the presence of an alkaline complex component to increase the concentration of CuCl2 in the solution and to thereby decrease the concentration of CuCl.

Elnited States Patent [191 Ruff [ METHOD OF PROCESSING A SPENT COPPER ETCHING SOLUTION FOR REUSE IN AN ELECTROLESS COPPER RECOVERY BATHS [75] Inventor: Claus Werner Ruff, Lichtenfels,

Germany [73} Assignee: Loewe-Opta GmbH, Berlin, Germany [22] Filed: Aug. 22, 1973 [21] Appl. No.1 390,553

[451 Dec. 17, 1974 [56] References Cited UNITED STATES PATENTS 3,438,901 4/1969 Vassileff 252/793 3,600,244 8/1971 Wegener 156/19 Primary EraminerWilliam A. Powell Attorney, Agent, or FirmArthur O. Klein [57] ABSTRACT 7 Process improvements are described for obtaining long term stability during the electroless recovery of etched copper from a spent acidic copper chloride 30 Foreign Application priority Data etching so1ution having a large concentration of a Se 1 9 1977 Germany 2244307 CuCl component. The spent solution is enriched by p l the addition of copper ions which are oxidized in the [57] Us Cl 252/792 156/19 252/794 presence of an alkaline complex component to in- 6 3 3/00 6 crease the concentration of CuCl in the solution and [58] Fie'ld 252/79 79 2 79 to thereby decrease the concentration of CuCl.

1 56/18, 19 4 Claims, 1 Drawing Figure 'flfl/ ffi OX/D/Z/WG m/r iii/Kr 5020/01 saui'cz l 7 15256590 fif/X/AG' M/X/AG 5 v5s2 v5s2 Y Aa icavffi) lEEIHiI 1. Z w i l 45 Cfi/VPAf/l /3 Ca/vPw/arr sawed:-

METHOD OF PROCESSING A SPENT COPPER ETCHING SOLUTION FOR REUSE IN AN ELE'CTROLESS COPPER RECOVERY BATI-IS BACKGROUND OF THE INVENTION During a typical copper etching operation which employs copper chloride in the form of CuCl in the starting solution along with the salt of an acid (e.g. HCl), at least a portion of the CuCI is converted into CuCl as metallic copper accumulates in the solution during the etch.

In order to advantageously employ auto-catalytic electroless techniques for recovery of the copper in the spent solution, a relatively low concentration of the saturated CuCl constituent should be present therein. Unfortunately, in the normal case the concentration of the saturated CuCl component is too high to produce sta ble long-term recovery of copper by the electroless method. As a result, it has been necessary as a practical matter to recover the copper directly from the spent etching solution by the use of relatively expensive electrolytic techniques, which in general require additional facilities for extracting impurities and other deposits from the electrolytic recovery bath.

SUMMARY OF THE INVENTION These drawbacks are eliminated in accordance with the invention, which contemplates an improved technique for preparing such spent copper etching solution for reuse in electroless regeneration of the etched copper present in the solution.

In an illustrative technique, the spent solution is first enriched by the addition of copper ions to a predetermined specified concentration. An oxidation medium (such as hydrogen peroxide) is then added to the enriched solution along with an alkaline complex component (illustratively ethylenediaminetetraacetic acid, hereinafter called EDTA) having a pH preferably in the range of 11.5 to 12.5. The resulting oxidation increases the CuClconstituent of the etching solution at the expense of the saturated CuCl constituent so that the solution may now be efficiently used for the electroless separation of copper.

BRIEF DESCRIPTION OF THE DRAWING The invention is further set forth in the following detailed description taken in conjunction with the appended drawing, in which the single FIGURE is a diagram showing facilities for preparing spent copper etching solution in accordance with the invention.

DETAILED DESCRIPTION A copper etching operation carried out in a conventional etching tank 1 may typically employ a starting solution that includes copper chloride (CuCl having a copper concentration in the range of 30 grams.

per liter, together with a salt of an acid such as HCl.

During the etching of copper from the work piece (not shown) in the tank 1 etched copper enters the solution and serves to transform a portion of the starting CuCl; constituent in the solution to CuCl in accordance with the reversible equation Cu CuC1 3 2 CuCl 2 CuCl 2 HCL H 0 2 CuCl 2 H 0 As the etch proceeds, however, the concentration of copper in the solution rises to a relatively high value (e.g., in the range of -140 grams per liter) and the solution becomes spent. At this point, the CuCl component is normally too large relative to the CuCl component to permit efficient electroless separation of the etched copper.

In-accordance with the invention, electroless recovery of the etched copper from the spent solution (which now contains constituents of CuCl, CuCl HCl, H 0 and H 0) is facilitated by the procedure to be described.

In particular, the spent solution from the etching tank 1 is conducted via a magnetic valve 2 and to a first mixing vessel 3 where it is enriched to a'prescribed copper concentration by theaddition of copper ions from a suitable source 11. At this point, the concentration of CuCl in the enriched solution may be analytically determined.

Next, an oxidizing agent (illustratively hydrogen peroxide) from a source 12 together with an alkaline complex component (illustratively EDTA) from a source 13 are then added to the enriched solution in a second mixing vessel 5. The resulting oxidation of the added copper serves to increase the concentration of the unsaturated CuCl component in the solution, in accordance with the following equation:

Cu 2 HC1+ H 0 cuci, H20

The relative amounts of the oxidizing agent and the alkaline complex component are determined in a conventional way in accordance with the previously measured concentration of CuCl in the enriched solution, although it has been found that when the oxidization agent is added in excess of such predetermined amount, improved performance is obtained in some cases Also, the EDTA added during the same step preferably has a pH in the range of 11.5 to 12.5 to prevent hydroxide formation. Care must be taken to assure that the elevated temperatures generates in the vessel 5 generated during oxidation does not impair the efficiency of the EDTA.

Other combined forms of oxygen (e.g., a chlorate) as well as free oxygen may be used as the oxidizing agent in the mixing vessel 5. Additionally, alkaline complex components other than EDTA (e.g., nitriloessic acid or triethanolamine) may be used.

From the vessel 5, the regenerated etching solution is applied through a filter 7 into an electroless copper recovery tank 8 (together with suitable stabilizers, if necessary.) whereupon efficient recovery of the etched copper from the regenerated, alkaline solution may be accomplished without the requirement of extraction of impurities and other contaminants as in electrolytic processes.

What is claimed is:

1. For use in the recovery of copper that is etched with the use of an acidic solution containing CuCl wherein a portion of the CuCl, is converted into CuCl during such etching operation as the solution becomes spent, a method of preparing the spent etching solution for reuse in the separation of the etched copper by electroless means which comprises the steps of:

adding copper ions to the spent solutionto a predetermined copper concentration suitable for electroless copper separation; and thereafter adding to the enriched solution an oxidizing agent and an alkaline complex component in amounts respectively effective to (1)- oxidize the added copper to increase the concentration of CuCl in the solution and correspondingly decrease the concentration of CuCl, and (2) to convert the etching solution into an alkaline bath.

2. A method as defined in claim 1, in which the alkaline complex component has a pH in the range between 11.5 and 12.5. 1

3. A method as defined in claim 1, in which the oxidizing agent is selected from the group consisting of hydrogen peroxide, free oxygen, and a chlorate.

4. A method as defined in claim 1, in which the alkaline complex component is selected from the group consisting of EDTA, nitriloessic acid and thriethanolamine. 1 

1. FOR USE IN THE RECOVERY OF COPPER THAT IS ETCHED WITH TTHE USE OF AN ACIDIC SOLUTION CONTAINING CUC12 WHEREIN A PORTION OF THE CUCI2 IS CONVERTED INTO CUCI DURING SUCH ETCHING OPERATION AS THE SOLUTION BECOMES SPENT, A METHOD OF PREPARING THE SPENT ETCHING SOLUTION FOR REUSE IN THE SPARATION OF THE ETCHED COPPER BY ELECTROLESS MEANS WHICH COMPRISES THE STEPS OF ADDING COPPER IONS TO THE SPENT SOLUTION TO A PREDETERMINED SEPARATION; AND THEREAFTER ADDING TO THE ENRICHED SOLUTION COPPER CONCENTRATION SUITABLE FOR ELECTROLESS COPPER AN OXIDIZING AGENT AND AN ALKALINE COMPLEX COMPONENT ON AMOUNTS RESPCTIVELY EFFECTIVE TO (1) OXIDIZE THE ADDED COPPER TO INCREASE THE CONCENTRATION OF CU-CI2 IN THE SOLUTION AND CORRESPO NDING DECREASE THE CONCENTRATION OF CUCI, AND (20 TO CONVERT THE ETCHING SOLUTION INTO AN ALKALINE BATH.
 2. A method as defined in claim 1, in which the alkaline complex component has a pH in the range between 11.5 and 12.5.
 3. A method as defined in claim 1, in which the oxidizing agent is selected from the group consisting of hydrogen peroxide, free oxygen, and a chlorate.
 4. A method as defined in claim 1, in which the alkaline complex component is selected from the group consisting of EDTA, nitriloessic acid and thriethanolamine. 